SUMMARY Serious adverse safety events that occur during the delivery of care are a leading cause of preventable death in the United States. The National Academy of Medicine recommends that hospitals and the EMS system ?implement evidence-based approaches to reduce errors in emergency and trauma care for children,? yet reports that a major barrier to such implementation is the ?paucity of high-quality data on the epidemiology of medical errors in children, particularly within the emergency care system.? Our initial NICHD-funded work (R01HD062478) demonstrated that critically-ill and injured children experience relatively high rates of adverse safety events in the prehospital setting in one major metropolitan area and that children experiencing out of hospital arrest (OHCA) may be at the highest risk for a life-threatening adverse safety event. This application leverages our expertise in prehospital patient safety with a goal to improve outcomes for pediatric OHCA, a leading cause of death in children. Despite advances leading to improved adult survival from OHCA, and pediatric in-hospital cardiac arrest no significant improvements have been observed in pediatric OHCA. The proposed research aims to improve pediatric OHCA resuscitation and outcomes. This application seeks to build a first-of-its-kind national pediatric OHCA safety registry, to examine the epidemiology of adverse safety events in pediatric OHCA, applies mixed methods, and exploits innovative technologies to identify contributing factors, potential mechanisms, and targets for interventions to reduce the occurrence of adverse safety events and improve outcomes for pediatric OHCA. Building on our prior work and leveraging our scientific expertise and relationships, we propose the following study aims: Aim 1) Measure and characterize the national prevalence of severe adverse events in pediatric OHCA and identify policies, practices and organizational features that are associated with these events. Aim 2) Apply simulation to examine how individual and team factors lead to adverse safety events Aim 3) Evaluate the impact of stress on providers? cognitive load and the occurrence of adverse safety events. This proposed research builds on our previous findings, creates a repository of preventable adverse safety events during pediatric OHCA care, and examines the impact of provider stress and cognitive load on errors.